Farm animal abortion Flashcards
Abortion definition
= birth before full term, of a dead or non-viable foetus
Stillbirth definition
= birth at full term, of a dead or non-viable foetus
Bovine abortion definition
= Expulsion of a foetus between the completion of differentiation (day 42) and the limit of foetal independent viability (day 265)
Why investigate abortions?
Economic impacts – calf, milk, AI, feed etc.
Wider significance or an easily solved problem?
▪ Public Health – zoonoses e.g. Salmonellosis
▪ Neospora – nearby footpaths
▪ Poor nutrition
Statutory Requirement – Brucellosis Order
▪ The legislation requires anyone in charge of bovine animals to report any abortion or premature calving (<271 days after service or <265 after implantation whether calf is dead or alive) within 24 hours.
▪ Suspicion of Brucella abortus must be reported to APHA in the same way as other notifiable diseases.
▪ Officially Brucellosis Free since 1985
▪ Scotland outbreak - 2003
▪ Cornwall outbreak – 2004
Is abortion the main cause of reproductive failure in cattle?
- no
What % of reproductive losses occur at <21d?
- ~75%
Approach to abortion cases
- history
- sampling
- list differentials (infectious vs non-infectious)
- biosecurity and zoonoses
- control/tx plan
Approach to abortion cases - history
▪ Individual vs multiple animals affected?
▪ Clinical signs in dams?
▪ Farm history
– Closed vs open? Recent purchases?
– Vaccination status?
– Recent management/diet changes?
– Previous test results/herd disease status – Current husbandry policies
▪ Foetus quality
▪ Decide an intervention figure
– Sporadic cases are less likely to be investigated & more likely to be non-infectious
– >3%?
Approach to abortion cases - sampling
- serology
- PM on foetus
Abortion diagnoses in cattle
- most diagnosed causes of abortion are infectious, but diagnostic rate is low
- Fetopathy/congenital disease - BVD 0.85%
- Salmonella NOS 0.35%
- Leptospira 0.10%
- IBR 0.06%
- Chlamydophila abortus 0.03%
- Salmonella Mbandaka 0.01%
- E. coli 0.68%
- Campylobacter NOS 0.51%
- S. Typhimurium 0.03%
- Traumatocia 0.12%
- Fungi NOS 1.17%
- Listeria 0.87%
- Schmallenberg virus 0.67%
- Coxiella burnetii 0.12%
- Dystokia 1.28%
- Bacillus licheniformis 2.07%
- Trueperella pyogenes 2.15%
- Diagnosis not listed 2.90%
- Neospora 2.98%
- S. dublin 2.99%
- Diagnosis not reached 80.06%
Abortion diagnoses in sheep
- S. Montevideo 0.79%
- Trueperella pyogenes 0.51%
- S. dublin 0.42%
- Fungi NOS 0.12%
- Bacillus licheniformis 0.30%
- Coxiella burnetii 0.06%
- S. Typhimurium 0.00%
- Yersinia spp. 0.43%
- Dystokia 1.01%
- Schmallenberg virus 1.71%
- Salmonella NOS 0.91%
- Listeria 1.95%
- Diagnosis not reached 49.76%
- Diagnosis not listed 4.44%
- Campylobacter NOS 8.17%
- Toxoplasma 11.73%
- Chlamydophila abortus 17.69%
Why are diagnostic rates low?
▪ Non-infectious causes
▪ Cost
▪ Limited farm history & data
▪ Sample quality & quantity
– No placenta
– Bacterial contaminant overgrowth
– Autolysis
– Cattle – time to abort
▪ Laboratory test limitations – only so many things can be tested for
▪ Sampling bias – some farmers sample every abortion, some only with a disaster
Manage expectations
▪ Foetus quality
▪ Client aims
– Decide an intervention figure
-> Sporadic cases are less likely to be investigated & more likely to be non- infectious
-> Intervention level 3 - 5% for outbreaks?
– Farm history – closed
-> Vaccinations
-> Dam Health
-> Previous test results
-> Herd disease status
-> Current husbandry policies
▪Current controls
▪ Previous investigations
Non-infectious causes
common in cattle, but difficult to prove
- Hereditary disorders/congenital defects
- Toxins
- Trauma
- Toxic
- Iatrogenic
- Concurrent dz
Non-infectious causes - hereditary disorders/congenital defects
- complex vertebral malformation
- dyschondroplasia
Non-infectious causes - toxins
- ergot
- nitrates/nitrites
- brassicae
- mycotoxins
- hemlock
- heavy metals
Non-infectious causes - trauma
- kick/crush injuries or transport
- hyperthermia
- twinning
Non-infectious causes - nutritional
- severe starvation
- pregnancy toxaemia
- vit A
- iodine
- selenium
- manganese
Non-infectious causes - iatrogenic
- prostaglandin
– endogenous (stress), inflammation, pyrexia; exogenous - dexamethasone
Non-infectious causes - concurrent dz
- liver fluke
- pneumonia
- Johne’s
- lungworm
Infectious causes in cattle - viral
▪ BVD
▪ IBR – BoHV-1
▪ Schmallenberg virus
▪ Bluetongue virus (NOTIFIABLE)
Infectious causes in cattle - Bacterial/Rickettsia
▪ Brucellosis (NOTIFIABLE & ZOONOTIC POTENTIAL)
▪ Leptospirosis (ZOONOTIC POTENTIAL)
▪ Salmonellosis (ZOONOTIC POTENTIAL)
▪ Bacillus licheniformis
▪ Listeria spp. (ZOONOTIC POTENTIAL)
▪ Coxiella burnetti (Q Fever) (ZOONOTIC POTENTIAL)
Infectious causes in cattle - fungal
- Aspergillus
- Absidia
- Rhizopus
Infectious causes in cattle - protozoal
- Neospora caninum
- Trichomoniasis
Infectious causes in cattle - sporadic causes
▪ Trueperella pyogenes
▪ E. coli (ZOONOTIC POTENTIAL)
▪ Histophilus somni
▪ TB (NOTIFIABLE & ZOONOTIC POTENTIAL)
Infectious causes in sheep - viral
▪ Border disease
▪ Bluetongue virus (NOTIFIABLE)
▪ Schmallenberg virus
Infectious causes in sheep - Bacterial/Rickettsia
▪ Chlamydophila abortus
▪ Campylobacter fetus fetus, Campylobacter jejuni
▪ Listeria spp.
▪ Salmonellosis
▪ Leptospirosis
▪ Brucellosis (NOTIFIABLE)
▪ Coxiella burnetti (Q Fever) – Rickettsia
▪ Tick Borne Fever - Anaplasma phagocytophilum
^ all bar tick borne fever have zoonotic potential
Infectious causes in sheep - protozoal
- Toxoplasma gondii (ZOONOTIC POTENTIAL)
Fresh sampling
▪ Placenta – cotyledon and surrounding membrane
– Detect fungi, C. abortus, C. burnetti, Brucella abortus
– Toxoplasma PCR
▪ Foetal stomach contents
– Bacteriology – aseptic
– Direct culture and selective culture (Salmonella,
Campylobacter, Brucella)
▪ Foetal fluid
– ‘Plain’ tube – serology
– BVD Ab/Ag, BDV Ab, Neospora Ab, Leptospirosis Ab, SBV Ab
▪ Lung
– can be used for culture
▪ Spleen
– BVD or BDV PCR
▪ Liver
– BoHV-1
– Trace mineral analysis
▪ Thyroid
– Iodine
▪ Hindbrain
– SBV PCR
Sampling to be fixed in formalin
▪ Placenta
▪ Brain
▪ Lung
▪ Trachea
▪ Liver
▪ Spleen
▪ Kidney
▪ Thyroid
▪ Heart
Sampling - maternal blood (paired?)
▪ Cattle serology
– BVDV (and PCR)
– Lepto
– Neospora
– IBR
– SBV
▪ Ovine serology
– EAE
– Toxoplasma
– Border disease (and PCR)
– SBV
Neospora caninum
▪ Protozoal parasite
▪ Canines are the definitive host but vertical transmission much more common
Neospora caninum transmission
Exogenous transmission
- Canine ingestion of tissue cysts e.g. in placenta
→ oocysts passed in faeces
→contaminate feed/water
→sporozoites in the intestinal tract
→tachyzoites in neural tissue, macrophages, hepatic cells, placenta, and others
→ bradyzoites primarily in neural tissue
▪ Vertical transmission from tachyzoites, via the placenta → foetus
Endogenous transmission
- Previously/persistently infected cow has reactivation of tissue
cysts
Signs of neospora caninum
▪ Abortion typically at 4-7 months but can cause resorptions, mummification, stillbirth, or may be born alive and persistently infected +/- congenital CNS disease
▪ Persistently infected calves grow to become persistently infected cows → 40-50% abort in their first year, or results in vertical transmission
Neospora caninum diagnosis
▪ Serology in cows
– Negative – rules out Neospora
– Positive – not diagnostic as not definitely the cause
-> If positive, statistically they are 6-7 times more likely to abort than those that are not
-> Antibody levels tend to be highest 10 to 4 weeks before calving
▪ PCR on foetal brain
▪ Histopathology +/- IHC on fixed brain
Neospora caninum prevention
▪ Infected dog faeces
▪ Remove access to placental material
▪ Test purchased cattle
▪ Avoid retaining breeding heifers born from seropositive cows
▪ Test and cull cows
Bovine Viral Diarrhoea (BVD)
▪ Pestivirus – BVDV-1 and BVDV-2 (BVDV-2 only really in the USA)
▪ Cytopathic and non-cytopathic strains
How BVD affects different stages of pregnancy
Infected cow → infected foetus
▪ Abortion can occur at any point in gestation (usually 1st/2nd trimester)
▪ 0-30 days – infertility or early embryonic death
▪ 18-125 days – PI calves
▪ 80-150 days – congenital defects e.g. cerebellar hypoplasia, cataracts, hydrocephalus etc.
▪ >150 days – the calf can launch an immune response and often survives
BVD Trojan cow
= non-PI cow carrying a PI calf
▪ Cow is antibody negative
BVD diagnosis
- lack of characteristic PM lesions
▪ PCR, antigen and antibody testing available
▪ PI calf – antigen positive, antibody negative
▪ PCR on aborted calf tissue (spleen often used)
▪ Antigen or antibody testing on blood (avoid antibody testing on post-colostral neonatal calves)
▪ Antigen/PCR testing on tissue in live animals e.g. ear tag
BVD control
- routine herd testing
- culling PIs
- vaccination
2 main types of Leptospira
- Leptospira borgpetersenii serovar Hardjo
- Leptospira interrogans serovar Hardjo
Are cattle at a higher risk of leptospirosis if grazing with sheep?
- yes
Leptospirosis CS
- infertility
- abortion usually >6m
- premature calves
- milk drop
Leptospirosis control & tx
▪ Vaccination
▪ Antibiotics – streptomycin, dihydrostreptomycin, oxytetracycline, amoxicillin ▪ Avoid grazing with sheep
Leptospirosis diagnosis
▪ usually no gross PM lesions
▪ PCR on foetal kidney, lung, or placenta
▪ Histopathology – foetal interstitial nephritis is pathognomonic
▪ Maternal serology – can be difficult to interpret
– Titres are often in decline by the time of abortion as abortion often occurs weeks to months after maternal infection
– Better used as a screening tool for the presence of lepto in the herd
Salmonella spp. in cattle
▪ PrimarilyS.Dublin- ~80%
Salmonella (cattle) CS
▪ Sporadic cause of abortion +/- dysentery and pyrexia in cows
Salmonella (cattle) - how is it introduced?
- introduction of carrier animals or contamination of feed/water
Salmonella (cattle) diagnosis
- culture from foetal stomach contents
▪ Serology may be useful, but titres fall rapidly after abortions
▪ Faecal culture from the dam has low sensitivity
▪ Cows that abort shed for a very short period of time compared to enteric cases where there is intermittent or continuous shedding
Salmonella (cattle) prevention
- vaccination
- destroy contaminated bedding
- isolate cows until vaginal discharge stops
Salmonella spp. in sheep
▪ Multiple strains - all, except S. abortusovis, are zoonotic
Salmonella (sheep) CS
▪ Ewes may be ill e.g. scour, metritis
▪ S. abortusovis
– few clinical signs other than abortion in the last 6 weeks of gestation
– Lambs may be born alive but die within the first week of life
▪ S. montevideo
– few clinical signs other than abortion
– no diarrhoea in lambs
▪ S. typhimurium
– pyrexia, anorexia
– profuse scour in ewes with foul smelling vaginal discharge
– May be fatal
– Lambs not aborted may be born stillbirth, or born alive and die soon after with evidence of scour
– Outbreaks often follow times of stress
▪ S. Dublin
– clinical signs similar to S. typhimurium but usually not as severe
Salmonella (sheep) diagnosis
- culture of foetal stomach contents
Salmonella (sheep) tx
- treat ewes with a sensitive antibiotic if necessary
Salmonella (sheep) prevention
- vaccination
- isolate aborted ewes
- avoid stress
Campylobacter spp. in cattle
- Campylobacter fetus subsp. venerealis
- Campylobacter fetus subsp. fetus
Both ^ cause abortions in cattle around 4-8m of gestation
Campylobacter fetus subsp. venerealis
▪ Cause of infertility and embryonic death primarily, associated with a mucopurulent endometritis
▪ Occasionally abortion at 4-8 months
▪ Venereal transmission
▪ Cows – fertility returns after 4-8 months once the uterus recovers
▪ Bulls – may recover or be infected for life. The older the bull, the more likely to be persistently infected
Campylobacter fetus subsp. venerealis - diagnosis
▪ Culture from vaginal washes or preputial scrapings/washes – difficult to culture successfully
▪ Vaginal Mucous Agglutination Test – picks up ~50% of positive cows
▪ Serology – very poor humoral response to venereal infection so of little value
Campylobacter fetus subsp. fetus
▪ Found in the intestinal tract → faeco-oral transmission
▪ Placental lesions – necrosis, intercotyledonary thickening and oedema, yellow-brown cotyledons
▪ Placental culture is difficult due to other contaminants overgrowing
– Foetal stomach contents – Campylobacter enrichment cultures
Campylobacter spp. in sheep
▪ Campylobacter fetus fetus – from carrier sheep
▪ C. jejuni from wildlife vectors
▪ Faeco-oral transmission → ewe to ewe transmission
Campylobacter spp. in sheep CS
▪ infection→abortion 7-25 days later, followed by strong immunity
▪ Abortion in the last 6 weeks of gestation and weak lambs born alive.
▪ May see diarrhoea as well as abortions.
▪ Up to 25% of ewes may abort in naïve flocks.
▪ Very few clinical signs in ewes other than abortion initially, though metritis may develop
▪ Aborted material is infectious
▪ Venereal spread not a feature (as in cattle – Campylobacter fetus venerealis)
▪ Can see waves of disease every 4-5 years as immunity wanes in individuals and through addition of naïve animals to the flock.
Campylobacter spp. in sheep diagnosis
▪ Placenta may have intercotyledonary oedema and cotyledonary necrosis
▪ Foetal livers may have multifocal areas of grey necrotic foci – pathognomonic
▪ Culture – foetal stomach contents (or placenta, or liver)
▪ Serology – not useful
Campylobacter spp. in sheep tx & prevention/control
▪ Antibiotics generally not effective
▪ Vaccines not licensed in the UK; serotype distributions in NZ are different to UK
▪ Some people will mix aborted ewes with lambed ewes to generate immunity
Toxoplasma gondii
▪ Protozoal parasite – infection is through ingestion of oocysts shed in cat faeces
▪ Zoonotic
▪ Cats are definitive host – sheep (and other mammals) are intermediate hosts
– Oocysts may survive for up to 2 years on pasture, feed, or bedding
– Up to 1 million oocysts per gram of cat faeces; as few as 200 needed to infect a ewe
Toxoplasma gondii CS
▪ Infection in non-pregnant sheep is usually asymptomatic but results in immunity.
▪ Ewes remain persistently infected for life but are immune so unlikely to abort again.
▪ Causes infertility, mummification, stillbirth and abortion depending on stage of gestation and infective dose.
▪ <60 days → foetal resorption → high barren rate if ram has been removed
▪ Mid-gestation → abortion or mummification
▪ >120 days → stillbirth, weak lambs, or normal lambs
Toxoplasma gondii diagnosis
– ‘frosted strawberry’ cotyledons
▪ Intercotyledonary areas unaffected (c.f. C. abortus) ▪ PCR – placenta
▪ Foetal serology – foetal fluid
▪ Maternal serology – antibodies can remain elevated for years (paired?)
Toxoplasma gondii control
- retain aborted ewes
- keep old neutered cats on farm
- vaccinate
Chlamydia abortus (EAE)
- Gram negative intracellular bacteria
- > 80% of outbreaks are from the purchase of infected ewes
- Bacteria are present in aborted material and venereal fluids, and can survive for weeks
Chlamydia abortus (EAE) CS/presentation
- Ewes infected early in pregnancy may abort this year. If non-pregnant or in late gestation (~>100d), they lie dormant until the next pregnancy.
- Results in late-term placentitis and abortion typically in the last 3 weeks of gestation.
- Some ewes become carriers and may excrete organism in their faeces.
Chlamydia abortus (EAE) diagnosis
▪ Ewes are not ill
▪ Intercotyledonary areas are thickened, leathery, and oedematous
▪ Necrosis of foetal cotyledons
▪ May get birth of weak lambs
▪ Smears from intercotyledonary areas are stained with a modified ZN stain → intracellular cocci seen
▪ Serology – maternal or foetal fluids
Chlamydia abortus (EAE) control
- retain ewes
- biosecurity
- vaccinate
- antibiosis?
Antibiotic usage for cases of EAE
- Oxytetracycline can help maintain the placenta in infected ewes to allow lambs to be born alive
- Must be given after 90 days (when the placenta starts to deteriorate) and before day 126 (3 weeks before lambing)
- If there are ewes 6-8 weeks off lambing (day 91-105) a dead vaccine (Inmeva) could be used. (Inmeva not recommended during last month of gestation)
- If <3 weeks from lambing, they may pick up C. abortus this year and abort next year.
- Can give live vaccine pre-tupping next year (will reduce abortions by ~50% in ‘pre-programmed’ ewes, but not prevent), or use antibiotics at day 91-126 in next gestation.
- Once a fully implemented vaccination protocol is in place antibiotics shouldn’t be required
General advice for abortions - immediate actions
▪ Isolate ewe (not required for toxo but a sensible precaution)
▪ Dispose of (if not being sampled) aborted material
▪ Treat systemic disease e.g. Salmonellosis
▪ Don’t foster on lambs (esp. ewe lambs that may be kept as replacements) to affected ewes (EAE risk)
▪ Mark ewes so that they can be identified for serology at a later date if required.
▪ Maintain good hygiene and biosecurity.
▪ Take disease specific actions e.g. prevent feed access for wild birds with C. jejuni
▪ Highlight zoonotic risk to farmer
General advice for abortions - future actions
▪ EAE – purchase accredited disease-free stock and keep separate until after first lambing
▪ Toxo – prevent transmission via the definitive host, i.e. keep cats out of feed stores.
▪ Vaccinate – EAE, Toxoplasmosis, Campylobacter (import), Salmonella abortusovis
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Vaccinations
Enzovax (MSD)
- live attenuated
- indications
– replacements >5m/o
– recommended to vaccinate between 4m and 1m before tupping
– many be administered with Toxovax at different sites
- duration: at least 3y
Cevac Chlamydia (Ceva):
- live attuenated
- indications
– replacements >5m/o
– recommended to vaccinate between 4m and 1m before tupping
– many be administered with Toxovax at different sites
- duration: not stated
Inmeva (Hip):
- inactivated
- indications:
– 2 doses, 3w apart, the 1st at least 5w before tupping
– can be used during pregnancy
– not recommended in the last month of pregnancy
- duration: annual booster 2w before mating required
Toxovax (MSD)
- live tachyzoites
- indications:
– replacements >5m/o
– should be vaccinated in the period from 4m to 3w prior to tupping
– may be given with live attenuated EAE vaccine at different sites
- duration: at least 2y
Live EAE or Toxo vaccine should not be used by women of childbearing age or immunocompromised individuals.
Schmallenberg virus
- An orthobunyavirus – spread mainly by culicoides midges affecting cattle and sheep
Schmallenberg virus CS
▪ May see pyrexia, diarrhoea, anorexia, milk drop
▪ Abortion and stillbirth, with congenital defects
– Arthrogryposis most common defect
– Neurological defects – hydrancephaly, hydrocephalus,
cerebellar hypoplasia, porencephaly
-> Think BTV.
Schmallenberg virus diagnosis
- limb defects are indicative ▪ Confirmation by PCR on brain
▪ Serology – maternal or foetal
Schmallenberg virus control
▪ Difficult – fly repellents or altering breeding season to avoid
vectors
▪ Dams develop long-lasting immunity
Why can concurrent disease cause abortion?
- due to stress and PG release
What is the most common cause of infectious abortion in cattle globally?
- Neospora caninum
Which species are asymptomatic carriers of leptospirosis?
- Sheep
Do you often have to treat leptospirosis?
- no
How does salmonella spread through herd?
- through discharge, placental material
What to do when PM calf for Schmallenberg virus
- remove brain for sampling and big hydrocephalus or fluid filled cavity
- have statutory requirement to notify APHA for potential testing for bluetongue as also causes these